Changing Offset

Hi those-in-the-know,
 
I have got hold of some 13x5.5" Globes that have a 29P offset.  The problem is that the 13x7" Hotwires I have have a 0 offset (or so I think - the rim is 204mm wide, approx 104mm from inner edge to backface).  Is there any way to make the Globes have a smaller offset?  I was hoping to get 185/60R13 or even 205/60R13 tyres on them, and I don't think I have quite enough room for the 185s - I think I'm stuck with 175/70R13s.
 
 I know wheel spacers are illegal, but is there any other hubs/mods that can be done to get the combo I'm after?  The hotwires will probably go back on in 12-18mths (after a good refurb), so hopefully nothing too drastic!
 
Cheers, Adam